The SEC adopted its long-awaited Regulation Best Interest, establishing new standard of conduct regulations for SEC-registered broker-dealers and their associated persons that are natural persons.  At the same time, the SEC adopted (i) a new relationship summary disclosure requirement, on Form CRS, for broker-dealers and investment advisers who offer services to retail investors and (ii) two interpretive releases—one on the investment adviser fiduciary duty and the other on the solely incidental exemption for broker-dealers from…